Fiddle Faddle / Violin’s Double? (or Fiddles VS. Violins: Duelling Trebles)

Avid Folk Alley listener, Robin Roderick, has an interesting question, one I’ve pondered, as well, for some time:

“Have you ever been compelled to find the answer to something that really doesn’t make any difference to you or anyone else, other than, perhaps, to increase your chances of winning at Trivial Pursuit? I’ve wondered, for many years now, just what, exactly, IS the difference between the VIOLIN and the FIDDLE? I’ve asked music teachers, and musicians alike. . . and have yet to hear a straightforward answer!

Does anyone out there in the folk alley have a clue, theory, or conjecture on the
subject? You can even begin with “Once upon a time. . . . ”

Let’s hear it, Fiddle fans – what’s your opinion or research on the subject?